function [status ] = mx_eyelink_send_message( msg )
%MX_EYELINK_SEND_MESSAGE Sends a text message the connected eye tracker. The 
% text will be added to the EDF file.
%
% Parameters:
% msg 	Text to send to the tracker.
% Returns:
% 0 if no error, else link error code.
%
%----------------------------------------------------------------------------
% Copyright Eduardo Aponte 2013
% aponteeduardo@gmail.com